cpm2: Implement GPIO LIB API on CPM2 Freescale SoC.

This patch implement GPIO LIB support for the CPM2 GPIOs. The code can
also be used for CPM1 GPIO port E, as both cores are compatible at the
register level.

Based on earlier work by Laurent Pinchart.

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Cc: Laurent Pinchart <laurentp@cse-semaphore.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>